Synthesis of 2-commodity flow networks

We investigate network design under volatile conditions of link failures and traffic overload. Our model is a nonsimultaneous 2-commodity problem. We characterize the feasible solutions and, using this characterization, we reduce the size of the linear program. For 0/1 requirements we present a closed fractional optimal solution, a closed integer-capacities optimal solution, and 7/6-approximation for the case in which integer 2-commodity flows are required.